linux-kernel - Re: [PATCH] include/linux/slab.h: new KFREE() macro.

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Date:	Tue, 09 Jan 2007 21:43:35 -0500
From:	Valdis.Kletnieks@...edu
To:	Amit Choudhary <amit2030@...oo.com>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Hua Zhong <hzhong@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] include/linux/slab.h: new KFREE() macro.

On Tue, 09 Jan 2007 16:00:51 PST, Amit Choudhary said:

> What did you understand when I wrote that "if you access the same memory again using the variable
> 'x"?
> 
> Using variable 'x' means using variable 'x' and not variable 'y'.

Right - but in real-world code, 'y' is the actual problem.

> Did I ever say that it fixes that kind of bug?

The point you're missing is that you're "fixing" a failure mode that in
general isn't seen, and ignoring the failure mode that *is* seen.

> Dereferencing 'x' means dereferencing 'x' and not dereferencing 'y'.

And neither "x" nor "y" is "the set of all still-live pointers to already-freed
memory" - which is why your proposal doesn't actually do anything effective.

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